Method of manufacture of a thermally actuated ink jet printer having a series of thermal actuator units

ABSTRACT

A method of manufacture of an ink jet print head arrangement including a series of nozzle chambers is disclosed, the method comprising the steps of: (a) utilizing an initial semiconductor wafer having an electrical circuitry layer formed thereon; (b) etching the electrical circuitry layer so as to define a nozzle chamber area; (c) depositing and etching a first sacrificial layer, the etching defining a series of nozzle chamber walls and an actuator anchor point; (d) depositing a first heater material layer; (e) depositing an intermediate material layer; (f) etching the first heater material layer and the intermediate material layer to define portions of actuator, ejection paddle and nozzle chamber walls; (g) depositing and etching a second sacrificial layer, the etching including etching a cavity defining a portion of the nozzle chamber walls; (h) depositing and etching a further glass layer to define the roof of the nozzle chamber and the walls thereof; (i) etching an ink supply channel through the wafer to form a fluid communication with the nozzle chamber; (j) etching away remaining sacrifical material.

CROSS REFERENCES TO REIATED APPLICATIONS

The following co-pending US patent applications, identified by their U.S. patent application Serial Numbers (U.S.S.N.), were filed simultaneously to the present application on Jul. 10, 1998, and are hereby incorporated by cross-reference.

09/113,060; 09/113,070; 09/113,073; 09/112,748; 09/112,747; 09/112,776; 09/112,750; 09/112,746; 09/112,743; 09/112,742; 09/112,741; 09/112,740; 09/112,739; 09/113,053; 09/112,738; 09/113,067; 09/113,063; 09/113,069; 09/112,744; 09/113,058; 09/112,777; 09/113,224; 09/112,804; 09/112,805; 09/113,072; 09/112,785; 09/112,797; 09/112,796; 09/113,071; 09/112,824; 09/113,090; 09/112,823; 09/113,222; 09/112,786; 09/113,051; 09/112,782; 09/113,056; 09/113,059; 09/113,091; 09/112,753; 09/113,055; 09/113,057; 09/113,054; 09/112,752; 09/112,759; 09/112,757; 09/112,758; 09/113,107; 09/112,829; 09/112,792; 09/112,791; 09/112,790; 09/112,789; 09/112,788; 09/112,795; 09/112,749; 09/112,784; 09/112,783; 09/112,763; 09/112,762; 09/112,737; 09/112,761; 09/113,223; 09/112,781; 09/113,052; 09/112,834; 09/113,103; 09/113,101; 09/112,751; 09/112,787; 09/112,802; 09/112,803; 09/113,097; 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821; 09/112,822; 09/112,825; 09/112,826; 09/112,827; 09/112,828; 09/113,111; 09/113,108; 09/113,109; 09/113,123; 09/113,114; 09/113,115; 09/113,129; 09/113,124; 09/113,125; 09/113,126; 09/113,119; 09/113,120; 09/113,221; 09/113,116; 09/113,118; 09/113,117; 09/113,113; 09/113,130; 09/113,110; 09/113,112; 09/113,087; 09/113,074; 09/113,089; 09/113,088; 09/112,771; 09/112,769; 09/112,770; 09/112,817; 09/113,076; 09/112,798; 09/112,801; 09/112,800; 09/112,799; 09/113,098; 09/112,833; 09/112,832; 09/112,831; 09/112,830; 09/112,836; 09/112,835; 09/113,102; 09/113,106; 09/113,105; 09/113,104; 09/112,810; 091112,766; 09/113,085; 09/113,086; 09/113,094; 09/112,760; 09/112,773; 09/112,774; 09/112,775; 09/112,745; 09/113,092; 09/113,100; 09/113,093; 09/113,062; 09/113,064; 09/113,082; 09/113,081; 09/113,080; 09/113,079; 09/113,065; 09/113,078; 09/113,075;

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the field of inkjet printers and discloses an inkjet printing system which includes a bend actuator interconnected into a paddle for the ejection of ink through an ink ejection nozzle. In particular, the present invention discloses a method of Manufacture of a thermally actuated ink jet printer having a series of thermal actuator units.

BACKGROUND OF THE INVENTION

Many ink jet printing mechanisms are known. Unfortunately, in mass production techniques, the production of ink jet heads is quite difficult For example, often, the orifice or nozzle plate is constructed separately from the ink supply and ink ejection mechanism and bonded to the mechanism at a later stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)). These separate material processing steps required in handling such precision devices often add a substantial expense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No. 4,899,181) are often used but again, this limits the amount of mass production throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilised. These can include electroforming of nickel stage (Hewlett-Packard Journal, Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laser ablation (U.S. Pat. No.5,208,604), micro-punching, etc.

The utilisation of the above techniques is likely to add substantial expense to the mass production of ink jet print heads and therefore add substantially to their final cost.

It would therefore be desirable if an efficient system for the mass production of ink jet print heads could be developed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for a method of manufacture of an ink ejection nozzle arrangement suitable for incorporation into an inkjet printhead arrangement for the ejection of ink on demand from a nozzle chamber in an efficient manner. In particular the ink jet printer can comprise a thermally actuated ink jet printer having a series of thermal actuator units.

In accordance with a first aspect of the present invention, there is provided a method of manufacture of a thermally actuated ink jet printer having a series of thermal actuator units wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes.

Multiple ink jet heads are preferably formed simultaneously on a single planar substrate. The substrate can be a silicon wafer. The print heads are preferably formed utilising standard vlsi/ulsi processing. Integrated drive electronics are preferably formed on the same substrate. The integrated drive electronics can be formed utilising a CMOS fabrication process.

Ink can be ejected from the substrate substantially normal to the substrate.

In accordance with a further aspect of the present invention, there is provided a method of manufacture of an ink jet print head arrangement including a series of nozzle chambers, the method comprising the steps of: (a) utilizing an initial semiconductor wafer having an electrical circuitry layer formed thereon; (b) etching the electrical circuitry layer so as to define a nozzle chamber area; (c) depositing and etching a first sacrificial layer, the etching defining a series of nozzle chamber walls and an actuator anchor point; (d) depositing a first heater material layer; (e) depositing an intermediate material layer; (f) etching the first heater material layer and the intermediate material layer to define portions of an actuator, ejection paddle and nozzle chamber walls; (g) depositing and etching a second sacrificial layer, the etching including etching a cavity defining a portion of the nozzle chamber walls; (h) depositing and etching a further glass layer to define the roof of the nozzle chamber and the walls thereof; (i) etching an ink supply channel through the wafer to form a fluid communication with the nozzle chamber; (j) etching away remaining sacrificial material.

The intermediate layer can comprise substantially glass. The first heater material layer can comprise substantially Titanium Nitride.

The steps further can include the step of etching anti-wicking notches in the surface of the circuitry layer.

Further, there is preferably included the step of depositing corrosion barriers over portions of the arrangement so as to reduce corrosion effects and the etching of layers preferably can includes etching vias so as to allow for the electrical interconnection of portions of subsequent layers. The wafer can comprise a double side polished CMOS wafer.

The step (j) can comprise a through wafer etch from a back surface of the wafer. The steps aforementioned are preferably also utilized to simultaneously separate the wafer into separate printheads.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIGS. 1-3 illustrate the basic operational principles of the preferred embodiment;

FIG. 4 is a side perspective view of a single inkjet nozzle arrangement constructed in accordance with the preferred embodiment;

FIG. 5 is a side perspective view of a portion of an array of a printhead constructed in accordance with the principles of the preferred embodiment;

FIG. 6 provides a legend of the materials indicated in FIG. 7 to 16; and

FIG. 7 to FIG. 16 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle;

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, there is provided a nozzle chamber having ink within it and a thermal actuator device interconnected to a paddle the thermal actuator device being actuated so as to eject ink from the nozzle chamber. The preferred embodiment includes a particular thermal actuator structure which includes a series of tapered actuator heater arms for providing conductive heating of a conductive trace. The actuator arm is interconnected to a paddle by a slotted wall in the nozzle chamber. The actuator arm has a mating shape so as to mate substantially with the surfaces of the slot in the nozzle chamber wall.

Turning initially to FIGS. 1-3, there is provided schematic illustrations of the basic operation of the device. A nozzle chamber 1 is provided filled with ink 2 by means of an ink inlet channel 3 which can be etched through a wafer substrate on which the nozzle chamber 1 rests. The nozzle chamber 1 further includes an ink ejection aperture 4 around which an ink meniscus 5 forms.

Inside the nozzle chamber 1 is a paddle type device 7 which is interconnected to an actuator arm 8 through a slot 22 (see FIG. 4) in the wall of the nozzle chamber 1. The actuator arm 8 includes a heater means e.g. 9 located adjacent to a post end portion 10 of the actuator arm, the post 10 being fixed to a substrate.

When it is desired to eject a drop from the nozzle chamber, as illustrated in FIG. 2, the heater means 9 is heated so as to undergo thermal expansion. Preferably, the heater means itself or the other portions of the actuator arm 8 are built from materials having a high bend efficiency where the bend efficiency is defined as ${{bend}\quad {efficiency}} = \frac{{{Young}'}s\quad {Modulus} \times \left( {{Coefficient}\quad {of}\quad {thermal}\quad {Expansion}} \right)}{{Density} \times {Specific}\quad {Heat}\quad {Capacity}}$

A suitable material for the heater elements is a copper nickel alloy which can be formed so as to bend a glass material.

The heater means is ideally located adjacent the post end portion 10 such that the effects of activation are magnified at the paddle end 30 such that small thermal expansions near post 10 result in large movements of the paddle end.

The heating 9 and consequential paddle movement causes a general increase in pressure around the ink meniscus 5 which expands, as illustrated in FIG. 2, in a rapid manner. The heater current is pulsed and ink is ejected out of the nozzle 4 in addition to flowing in from the ink channel 3.

Subsequently, the paddle 7 is deactivated to again return to its quiescent position. The deactivation causes a general reflow of the ink into the nozzle chamber. The forward momentum of the ink outside the nozzle rim and the corresponding backflow results in a general necking and breaking off of the drop 12 which proceeds to the print media. The collapsed meniscus 5 results in a general sucking of ink into the nozzle chamber 2 via the in flow channel 3. In time, the nozzle chamber is refilled such that the position in FIG. 1 is again reached and the nozzle chamber is subsequently ready for the ejection of another drop of ink.

Turning now to FIG. 4 there is illustrated a view of a single nozzle arrangements of the preferred embodiment. The arrangement of FIG. 4 has a number of structures which aid and assist in the low energy operation of the paddle.

Firstly, the actuator 8 includes a series of tapered heater sections 15 each of which comprises an upper glass portion (amorphous silicon dioxide) 16 formed on top of a titanium nitride layer 17. Alternatively a copper nickel alloy layer (hereinafter called cupronickel) can be utilized which will have a higher bend efficiency where bend efficiency is defined as: ${{bend}\quad {efficiency}} = \frac{{{Young}'}s\quad {Modulus} \times \left( {{Coefficient}\quad {of}\quad {thermal}\quad {Expansion}} \right)}{{Density} \times {Specific}\quad {Heat}\quad {Capacity}}$

The titanium nitride layer 17 is in a tapered form and, as such, resistive heating takes place near the post end portion 10. Adjacent titanium nitride/glass portions are interconnected at block portion 19 which also provides for a mechanical structural support for the actuator arm.

The heater sections 15 ideally are tapered and are elongated and spaced apart such that, upon heating, the bending force exhibited along the axis of the actuator arm is maximized. The slots between adjacent tapered portions allow for slight differential operation of each thermal actuator with respect to adjacent actuators.

The block portion 19 is interconnected to an arm portion 20. The arm 20 is in turn connected to the paddle 7 inside the nozzle chamber 1 by means of a slot e.g. 22 formed in the side of the nozzle chamber 1. The formation of the slot 22 is designed generally to mate with the surfaces of the arm 20 so as to minimise opportunities for the outflow of ink around this arm. The ink is held generally within the nozzle chamber 1 via surface tension effects around the slot 22.

When it is desired to actuate the arm 8, a conductive current is passed through the titanium nitride layer 17 via vias within the block portion 10 connecting to a lower CMOS layer 6 which provides for the necessary power and control circuitry for the nozzle arrangement. The conductive current results in heating of the nitride layer 17 adjacent to the post portion 10 which results in a general upward bending of the arm 8 and the consequential ejection of ink out of the nozzle 4. The ejected drop is printed on page in the usual manner for an inkjet printer as previously described.

Obviously, an array of ink ejection devices can be subsequently formed so as to create a single printhead. For example, in FIG. 5 there is illustrated an array which comprises multiple ink ejection nozzle arrangements 1 laid out in interleaved lines so as to form a printhead array. Of course, different types of arrays can be formulated including full color arrays etc.

The preferred embodiment achieves a particular balance between utilisation of the standard semi-conductor processing material such as titanium nitride and glass in a MEMS process. Obviously the skilled person may make other choices of materials and design features where the economics are justified. For example, a copper nickel alloy of 50% copper and 50% nickel may be more advantageously deployed as the conductive heating compound as it is likely to have higher levels of bend efficiency. Also, other design structures may be employed where it is not necessary to provide for such a simple form of manufacture.

One form of detailed manufacturing process which can be used to fabricate monolithic ink jet print heads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double sided polished wafer 31, complete a 0.5 micron, one poly, 2 metal CMOS process to form layer 6. This step is shown in FIG. 7. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 6 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.

2. Etch oxide layer 6 down to silicon or aluminum 32 using Mask 1. This mask defines the nozzle chamber, the surface anti-wicking notch, and the heater contacts. This step is shown in FIG. 8.

3. Deposit 1 micron of sacrificial material 33 (e.g. aluminum or photosensitive polyimide)

4. Etch (if aluminum) or develop (if photosensitive polyimide) the sacrificial layer 33 using Mask 2. This mask defines the nozzle chamber walls and the actuator anchor point. This step is shown in FIG. 9.

5. Deposit 0.2 micron of heater material 34, e.g. TiN.

6. Deposit 3.4 microns of PECVD glass 35.

7. Etch both glass 35 and heater 34 layers together, using Mask 3. This mask defines the actuator, paddle, and nozzle chamber walls. This step is shown in FIG. 10.

8. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.

9. Deposit 10 microns of sacrificial material 36.

10. Etch or develop sacrificial material 36 using Mask 4. This mask defines the nozzle chamber wall. This step is shown in FIG. 11.

11. Deposit 3 microns of PECVD glass 37.

12. Etch to a depth of (approx.) 1 micron using Mask 5. This mask defines the nozzle rim 38. This step is shown in FIG. 12.

13. Etch down to the sacrificial layer 36 using Mask 6. This mask defines the roof of the nozzle chamber, and the nozzle 4 itself. This step is shown in FIG. 13.

14. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 7. This mask defines the ink inlets 3 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 14.

15. Etch the sacrificial material 33, 36. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 15.

16. Mount the print heads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets 3 at the back of the wafer.

17. Connect the print heads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

18. Hydrophobize the front surface of the print heads.

19. Fill the completed print heads with ink 39 and test them. A filled nozzle is shown in FIG. 16.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing system including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with in-built pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Ink Jet Technologies The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal inkjet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal inkjet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric inkjet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per print head, but is a major impediment to the fabrication of pagewidth print heads with 19,200 nozzles.

Ideally, the inkjet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new inkjet technologies have been created. The target features include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the inkjet systems described below with differing levels of difficulty. Forty-five different inkjet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the list under the heading “Cross-References to Related Applications”.

The inljet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems

For ease of manufacture using standard process equipment, the print head is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the print head is 100 mm long, with a width which depends upon the inkjet type. The smallest print head designed is U.S. patent application Ser. No. 09/112,764, which is 0.35 mm wide, giving a chip area of 35 square mm. The print heads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the print head by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The print head is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

The present invention is useful in the field of digital printing, in particular, ink jet printing. A number of patent applications in this field were filed simultaneously and incorporated by cross reference.

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. Forty-five such inkjet types were filed simultaneously to the present application.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the forty-five examples can be made into ink jet print heads with characteristics superior to any currently available ink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The simultaneously filed patent applications by the present applicant are listed by USSN numbers. In some cases, a print technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix are set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal An electrothermal heater heats the ♦ Large force generated ♦ High power ♦ Canon Bubblejet bubble ink to above boiling point, ♦ Simple construction ♦ Ink carrier limited to water 1979 Endo et al GB transferring significant heat to the ♦ No moving parts ♦ Low efficiency patent 2,007,162 aqueous ink. A bubble nucleates and ♦ Fast operation ♦ High temperatures required ♦ Xerox heater-in- quickly forms, expelling the ink. ♦ Small chip area required for ♦ High mechanical stress pit 1990 Hawkins et The efficiency of the process is low, actuator ♦ Unusual materials required al U.S. Pat. No. with typically less than 0.05% of the ♦ Large drice trasistors 4,899,181 electrical energy being transformed ♦ Cavitation causes actuator failure ♦ Hewlett-Packard into kinetic energy of the drop. ♦ Kogation reduces bubble formation TIJ 1982 Vaught et ♦ Large print heads are difficult to al U.S. Pat. No. fabricate 4,490,728 Piezoelectric A piezoelectric crystal such as lead ♦ Low power consumption ♦ Very large area required for actuator ♦ Kyser et al U.S. lanthanum zirconate (PZT) is ♦ Many ink types can be used ♦ Difficult to integrate with electronics Pat. No. 3,946,398 electrically activated, and either ♦ Fast operation ♦ High voltage drive transistors required ♦ Zoltan U.S. expands, shears, or bends to apply ♦ High efficiency ♦ Full pagewidth print heads impractical Pat. No. 3,683,212 pressure to the ink, ejecting drops. due to actuator size ♦ 1973 Stemme ♦ Requires electrical poling in high field U.S. Pat. No. strengths during manufacture 3,747,120 ♦ Epson Stylus ♦ Tektronix ♦ USSN 09/112,803 Electro- An electric field is used to activate ♦ Low power consumption ♦ Low maximum strain (approx. 0.01%) ♦ Seiko Epson, strictive electrostriction in relaxor materials ♦ Many ink types can be used ♦ Large area required for actuator due to Usui et al. JP such as lead lanthanum zirconate ♦ Low thermal expansion low strain 253401/96 titanate (PLZT) or lead magnesium ♦ Electric field strength ♦ Response speed is marginal (˜10 μs) ♦ USSN niobate (PMN). required (approx. 3.5 V/μm) ♦ High voltage drive transistors required 09/112,803 can be generated without ♦ Full pagewidth print heads impractical difficulty due to actuator size ♦ Does not require electrical poling Ferroelectric An electric field is used to induce a ♦ Low power consumption ♦ Difficult to integrate with electronics ♦ USSN phase transition between the ♦ Many ink types can be used ♦ Unusual materials such as PLZSnT are 09/112,803 antiferroelectric (AFE) and ♦ Fast operation (<1 μs) required ferroelectric (FE) phase. Perovskite ♦ Relatively high longitudinal ♦ Actuators require a large area materials such as tin modified lead strain lanthanum zirconate titanate ♦ High efficiency (PLZSnT) exhibit large strains of up ♦ Electric field strength of to 1% associated with the AFE to FE around 3 V/μm can be phase transition. readily provided Electrostatic Conductive plates are separated by a ♦ Low power consumption ♦ Difficult to operate electrostatic ♦ USSN plates compressible or fluid dielectric ♦ Many ink types can be used devices in an aqueous environment 09/112,787; (usually air). Upon application of a ♦ Fast operation ♦ The electrostatic actuator will normally 09/112,803 voltage, the plates attract each other need to be separated from the ink and displace ink, causing drop ♦ Very large area required to achieve ejection. The conductive plates may high forces be in a comb or honeycomb ♦ High voltage drive transistors may be structure, or stacked to increase the required surface area and therefore the force. ♦ Full pagewidth print heads are not competitive due to actuator size Electrostatic A strong electric field is applied to ♦ Low current consumption ♦ High voltage required ♦ 1989 Saito et al, pull on ink the ink, whereupon electrostatic ♦ Low temperature ♦ May be damaged by sparks due to air U.S. Pat. No. attraction accelerates the ink towards breakdown 4,799,068 the print medium. ♦ Required field strength increases as the ♦ 1989 Miura et al, drop size decreases U.S. Pat. No. ♦ High voltage drive transistors required 4,810,954 ♦ Electrostatic field attracts dust ♦ Tonejet Permanent An electromagnet directly attracts a ♦ Low power consumption ♦ Complex fabrication ♦ USSN magnet permanent magnet, displacing ink ♦ Many ink types can be used ♦ Permanent magnetic material such as 09/113,084; electro- and causing drop ejection. Rare earth ♦ Fast operation Neodymium Iron Boron (NdFeB) 09/112,779 magnetic magnets with a field strength around ♦ High efficiency required. 1 Tesla can be used. Examples are: ♦ Easy extension from single ♦ High local currents required Samarium Cobalt (SaCo) and nozzles to pagewidth print ♦ Copper metalization should be used for magnetic materials in the heads long electromigration lifetime and low neodymium iron boron family resistivity (NdFeB, NdDyFeBNb, NdDyFeB, ♦ Pigmented inks are usually infeasible etc) ♦ Operating temperature limited to the Curie temperature (around 540 K.) Soft A solenoid induced a magnetic field ♦ Low power consumption ♦ Complex fabrication USSN 09/112,751; magnetic in a soft magnetic core or yoke ♦ Many ink types can be used ♦ Materials not usually present in a 09/113,097; core electro- fabricated from a ferrous material ♦ Fast operation CMOS fab such as NiFe, CoNiFe, or 09/113,066; magnetic such as electroplated iron alloys such ♦ High efficiency CoFe are required 09/112,779; as CoNiFe [1], CoFe, or NiFe alloys. ♦ Easy extension from single 09/113,061; Typically, the soft magnetic material nozzles to pagewidth print ♦ Copper metalization should be used for 09/112,816; is in two parts, which are normally heads long electromigration lifetime and low 09/112,772; held apart by a spring. When the resistivity 09/112,815 solenoid is actuated, the tow parts ♦ Electroplating is required attract, displacing the ink. ♦ High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz force The Lorenz force acting on a current ♦ Low power consumption ♦ Force acts as a twisting motion USSN 09/113,099; carrying wire in a magnetic field is ♦ Many ink types can be used ♦ Typically, only a quarter of the 09/113,077; utilized. ♦ Fast operation solenoid length provides force in a 09/112,818; This allows the magnetic field to be ♦ High efficiency useful direction 09/112,819 supplied externally to the print head, ♦ Easy extension from single ♦ High local currents required for example with rare earth nozzles to pagewidth print ♦ Copper metalization should be used for permanent magnets. heads long electromigration lifetime and low Only the current carrying wire need resistivity be fabricated on the print-head, ♦ Pigmented inks are usually infeasible simplifying materials requirements. Magneto- The actuator uses the giant ♦0 Many ink types can be used ♦ Force acts as a twisting motion ♦ Fischenbeck, striction magnetostrictive effect of materials ♦ Fast operation ♦ Unusual materials such as Terfenol-D U.S. Pat. No. such as Terfenol-D (an alloy of ♦ Easy extension from single are required ♦ USSN terbium, dysprosium and iron nozzles to pagewidth print ♦ High local currents required 09/113,121 developed at the Naval Ordnance heads ♦ Copper metalization should be used for Laboratory, hence Ter-Fe-NOL). For ♦ High force is available long electromigration lifetime and low best efficiency, the actuator should resistivity be pre-stressed to approx. 8 MPa. Surface Ink under positive pressure is held in ♦ Low power consumption ♦ Requires supplementary force to effect ♦ Silverbrook, EP tension a nozzle by surface tension. The ♦ Simple construction drop separation 0771 658 A2 and reduction surface tension of the ink is reduced ♦ No unusual materials ♦ Requires special ink surfactants related patent below the bubble threshold, causing required in fabrication ♦ Speed may be limited by surfactant applications the ink to egress from the nozzle. ♦ High efficiency properties nozzles to pagewidth print heads Viscosity The ink viscosity is locally reduced ♦ Simple construction ♦ Requires supplementary force to effect ♦ Silverbrook, EP reduction to select which drops are to be ♦ No unusual materials drop separation 0771 658 A2 and ejected. A viscosity reduction can be required in fabrication ♦ Requires special ink viscosity related patent achieved electrothermally with most ♦ Easy extension from single properties applications inks, but special inks can be nozzles to pagewidth print ♦ High speed is difficult ot achieve engineered for a 100:1 viscosity heads ♦ Requires oscillating ink pressure reduction. ♦ A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave is generated and ♦ Can operate without a ♦ Complex drive circuitry ♦ 1993 Hadimioglu focussed upon the drop ejection nozzle plate ♦ Complex fabrication et al, EUP 550,192 region. ♦ Low efficiency ♦ 1993 Elrod et al, ♦ Poor control of drop position EUP 572,220 ♦ Poor control of drop volume Thermo- An actuator which relies upon ♦ Low power consumption ♦ Efficient aqueous operation requires a ♦ USSN elastic bend differential thermal expansion upon ♦ Many ink types can be used thermal insulator on the hot side 09/112,802; actuator Joule heating is used. ♦ Simple planar fabrication ♦ Corrosion prevention can be difficult 09/112,778; ♦ Small chip area required for ♦ Pigmented inks may be infeasible, as 09/112,815; each actuator pigment particles may jam the bend 09/113,096; ♦ Fast operation actuator 09/113,068; ♦ High efficiency 09/113,095; ♦ CMOS compatible voltages 09/112,808; and currents 09/112,809; ♦ Standard MEMS processes 09/112,780; can be used 09/113,083; ♦ Easy extension from single 09/112,793; nozzles to pagewidth print 09/112,794; heads 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768 High CTE A material with a very high ♦ High force can be generated ♦ Requires special material (e.g. PTFE) ♦ USSN thermoelastic coefficient of thermal expansion ♦ Three methods of PTFE ♦ Requires a PTFE deposition process, 09/112,778; actuator (CTE such as deposition are under which is not yet standard in ULSI fabs 09/112,815; polytetrafluoroethylene (PTFE) is development: chemical ♦ PTFE depostion cannot be followed 09/113,096; used. As high CTE material are vapor deposition (CVD), with high temperature (above 350° C.) 09/113,095; usually non-conductive, a heater spin coating, and processing 09/112,808; fabricated from a conductive evaporation ♦ Pigmented inks may be infeasible, as 09/112,809; material is incorporated. A 50 μm ♦ PTFE is a candidate for low pigment particles may jam the bend 09/112,780; long PTFE bend actuator with dielectric constant actuator 09/113,083; polysilicon heater and 15 mW power insulation in ULSI 09/112,793; input can provide 180 μN force and ♦ Very low power 09/112,794; 10 μm deflection. Actuator motions consumption 09/113,128; include: ♦ Many ink types can be used 09/113,127; Bend ♦ Simple planar fabrication 09/112,756; Push ♦ Small chip area required for 09/112,807; Buckle each actuator 09/112,806; Rotate ♦ Fast operation 09/112,820 ♦ High efficiency ♦ CMOS compatible voltages and currents ♦ Easy extension from single nozzles to pagewidth print heads Conductive A polymer with a high coefficient of ♦ High force can be generated ♦ Requires special materials ♦ USSN polymer thermal expansion (such as PTFE) is ♦ Very low power development (High CTE conductive 09/113,083 thermoelatic doped with conducting substances to consumption polymer) actuator increase its conductivity it about 3 ♦ Many ink types can be used ♦ Requires a PTFE deposition process, orders of magnitude below that of ♦ Simple planar fabrication which is not yet standard in ULSI fabs copper. The conducting polymer ♦ Small chip area required for ♦ PTFE deposition cannot be followed expands when resistively heated. each actuator with high temperature (above 350° C.) Examples of conducting dopants ♦ Fast operation processing include: ♦ High efficiency ♦ Evaporation and CVD deposition Carbon nanotubes ♦ CMOS compatible voltages techniques cannot be used Metal fibers and currents ♦ Pigmented inks may be infeasible, as Conductive polymers such as ♦ Easy extension from single pigment particles may jam the bend doped polythiophene nozzles to pagewidth print actuator Carbon granules heads Shape A shape memory alloy such as TiNi ♦ High force is available ♦ Fatigue limits maximum number of ♦ USSN memory (also know as Nitinol - Nickel (stresses of hundreds of cycles 09/113,122 alloy Titanium alloy developed at the MPa) ♦ Low strain (1%) is required to extend Naval Ordnance Laboratory) is ♦ Large strain is available fatigue resistance thermally switched between its weak (more than 3%) ♦ Cycle rate limited by heat removal martensitic state and its high ♦ High corrosion resistance ♦ Requires unusual materials (TiNi) stiffness austenic state. The shape of ♦ Simple construction ♦ The latent heat of transformation must the actuator in its martensitic state is ♦ Easy extension from sing be provided deformed relative to the austenic nozzles to pagewidth print ♦ High current operation shape. The shape change causes heads ♦ Requires pre-stressing to distort the ejection of a drop. ♦ Low voltage operation martensitic state Linear Linear magnetic actuators include ♦ Linear Magnetic actuators ♦ Requires unusual semiconductor ♦ USSN Magnetic the Linear Induction Actuator (LIA), can be contructed with materials such as soft magnetic alloys 09/113,061 Actuator Linear Permanent Magnet high thrust, long travel, and (e.g. CoNiFe) Synchronous Actuator (LPMSA), high efficiency using planar ♦ Some varieties also require permanent Linear Reluctance Synchronous semiconductor fabrication magnetic materials such as Actuator (LRSA), Linear Switched techniques Neodymium iron boron (NdFeB) Reluctance Actuator (LSRA), and ♦ Long actuator travel is ♦ Requires complex multi-phase drive the Linear Stepper Actuator (LSA). available circuitry ♦ Medium force is available ♦ High current operation ♦ Low voltage operation

BASIC OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the simplest mode of ♦ Simple operation ♦ Drop repetition rate is usually limited ♦ Thermal ink jet directly operation: the actuator directly ♦ No external fields required to around 10 kHz. However, this is ♦ Piezoelectric ink jet pushes ink supplies sufficient kinetic energy to ♦ Satellite drops can be not fundamental to the method, but is ♦ USSN 09/112,751; expel the drop. The drop must have a avoided if drop velocity is related to the refill method normally 09/112,787; 09/112,802; sufficient velocity to overcome the less than 4 m/s used 09/112,803; 09/113,097; surface tension. ♦ Can be efficient, depending ♦ All of the drop kinetic energy must 09/113,099; 09/113,084; upon the actuator used be provided by the actuator 09/112,778; 09/113,077; ♦ Satellite drops usually form if drop 09/113,061; 09/112,816; velocity is greater than 4.5 m/s 09/112,819; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Proximity The drops to be printed are selected ♦ Very simple print head ♦ Requires close proximity between the ♦ Silverbrook, EP 0771 by some manner (e.g. thermally fabrication can be used print head and the print media or 658 A2 and related induced surface tension reduction of ♦ The drop selection means transfer roller patent applications pressurized ink). Selected drops are does not need to provide the ♦ May require two print heads printing separated from the ink in the nozzle energy required to separate alternate rows of the image by contact with the print medium or the drop from the nozzle ♦ Monolithic color print heads are a transfer roller. difficult Electrostatic The drops to be printed are selected ♦ Very simple print head ♦ Requires very high electrostatic field ♦ Silverbrook, EP 0771 pull on ink by some manner (e.g. thermally fabrication can be used ♦ Electrostatic field for small nozzle 658 A2 and related induced surface tension reduction of ♦ The drop selection means sizes is above air breakdown patent applications pressurized ink). Selected drops are does not need to provide the ♦ Electrostatic field may attract dust ♦ Tone-Jet separated from the ink in the nozzle energy required to separate by a strong electric field. the drop from the nozzle Magnetic The drops to be printed are selected ♦ Very simple print head ♦ Requires magnetic ink ♦ Silverbrook, EP 0771 pull on ink by some manner (e.g. thermally fabrication can be used ♦ Ink colors other than black are 658 A2 and related induced surface tension reduction of ♦ The drop selection means difficult patent applications pressurized ink). Selected drops are does not need to provide the ♦ Requires very high magnetic separated from the ink in the nozzle energy required to separate fields by a strong magnetic field acting on the drop from the nozzle the magnetic ink. Shutter The actuator moves a shutter to ♦ High speed (>50 kHz) ♦ Moving parts are required ♦ USSN 09/112,818 block ink flow to the nozzle. The ink operation can be achieved ♦ Requires ink pressure modulator 09/112,815; 09/112,808 pressure is pulsed at a multiple of the due to reduced refill time ♦ Friction and wear must be considered drop ejection frequency. ♦ Drop timing can be very ♦ Stiction is possible accurate ♦ The actuator energy can be very low Shuttered The actuator moves a shutter to ♦ Actuators with small travel ♦ Moving parts are required ♦ USSN 09/113,066; grill block ink flow through a grill to the can be used ♦ Requires ink pressure modulator 09/112,772; 09/113,096; nozzle. The shutter movement need ♦ Actuators with small force ♦ Friction and wear must be considered 09/113,068 only be equal to the width of the grill can be used ♦ Stiction is possible holes. ♦ High speed (>50 kHz) operation can be achieved Pulsed A pulsed magnetic field attracts an ♦ Extremely low energy ♦ Requires an external pulsed magnetic ♦ USSN 09/112,779 magnetic ‘ink pusher’ at the drop ejection operation is possible field pull on ink frequency. An actuator controls a ♦ No heat dissipation ♦ Requires special materials for both pusher catch, which prevents the ink pusher problems the actuator and the ink pusher from moving when a drop is not to ♦ Complex construction be ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator directly fires the ink ♦ Simplicity of construction ♦ Drop ejection energy must be ♦ Most ink jets, drop, and there is no external field or ♦ Simplicity of operation supplied by individual nozzle actuator including other mechanism required. ♦ Small physical size piezoelectric and thermal bubble. ♦ USSN 09/112,751; 09/112,787; 09/112,802; 09/112,803; 09/113,097; 09/113,084; 09/113,078; 09/113,077; 09/113,061; 09/112,816; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Oscillating The ink pressure oscillates, ♦ Oscillating ink pressure can ♦ Requires external ink pressure ♦ Silverbrook, EP 0771 ink pressure providing much of the drop ejection provide a refill pulse, oscillator 658 A2 and related (including energy. The actuator selects which allowing higher operating ♦ Ink pressure phase and amplitude patent applications acoustic drops are to be fired by selectively speed must be carefully controlled ♦ USSN 09/113,066; stimulation) blocking or enabling nozzles. The ♦ The actuators may operate ♦ Acoustic reflections in the ink 09/112,818; 09/112,772; ink pressure oscillation may be with much lower energy chamber must be designed for 09/112,815; 09/113.096; achieved by vibrating the print head, ♦ Acoustic lenses can be used 09/113,068; 09/112,808 or preferably by an actuator in the to focus the sound on the ink supply. nozzles Media The print head is placed in close ♦ Low power ♦ Precision assembly required ♦ Silverbrook, EP 0771 proximity proximity to the print medium. ♦ High accuracy ♦ Paper fibers may cause problems 658 A2 and related Selected drops protrude from the ♦ Simple print head ♦ Cannot print on rough substrates patent applications print head further than unselected construction drops, and contact the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed to a transfer roller ♦ High accuracy ♦ Bulky ♦ Silverbrook, EP 0771 roller instead of straight to the print ♦ Wide range of print ♦ Expensive 658 A2 and related medium A transfer roller can also be substrates can be used ♦ Complex construction patent applications used for proximity drop separation. ♦ Ink can be dried on the ♦ Tektronix hot melt transfer roller piezoelectric ink jet ♦ Any of USSN 09/112,751; 09/112,787; 09/112,802; 09/112,803; 09/113,097; 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Electrostatic An electric field is used to accelerate ♦ Low power ♦ Field strength required for separation ♦ Silverbrook, EP 0771 selected drops towards the print ♦ Simple print head of small drops is near or above air 658 A2 and related medium. construction breakdown patent applications ♦ Tone-Jet Direct A magnetic field is used to accelerate ♦ Low power ♦ Requires magnetic ink ♦ Silverbrook, EP 0771 magnetic selected drops of magnetic ink ♦ Simple print head ♦ Requires strong magnetic field 658 A2 and related field towards the print medium. construction patent applications Cross The print head is placed in a constant ♦ Does not require magnetic ♦ Requires external magnet ♦ USSN 09/113,099; magnetic magnetic field. The Lorenz force in a materials to be integrated in ♦ Current densities may be high, 09/112,819 field current carrying wire is used to move the print head resulting in electromigration problems the actuator. manufacturing process Pulsed A pulsed magnetic field is used to ♦ Very low power operation ♦ Complex print head construction ♦ USSN 09/112,779 magnetic cyclically attract a paddle, which is possible ♦ Magnetic materials required in print field pushes on the ink. A small actuator ♦ Small print head size head moves a catch, which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator mechanical ♦ Operational simplicity ♦ Many actuator mechanisms have ♦ Thermal Bubble amplification is used. The actuator insufficient travel, or insufficient force, Ink jet directly drives the drop ejection to efficiently drive the drop ejection ♦ USSN 09/112,751; process. process 09/112,787; 09/113,099; 09/113,084; 09/112,819; 09/113,121; 09/113,122 Differential An actuator material expands more ♦ Provides greater travel in a ♦ High stresses are involved ♦ Piezoelectric expansion on one side than on the other. The reduced print head area ♦ Care must be taken that the materials ♦ USSN 09/112,802; bend expansion may be thermal, do not delaminate 09/112,778; 09/112,815; actuator piezoelectric, magnetostrictive, or ♦ Residual bend resulting from high 09/113,096; 09/113,068; other mechanism. temperature or high stress during 09/113,095; 09/112,808; The bend actuator converts a high formation 09/112,809; 09/112,780; force low travel actuator mechanism 09/113,083; 09/112,793; to high travel, lower force 09/113,128; 09/113,127; mechanism. 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Transient A trilayer bend actuator where the ♦ Very good temperature ♦ High stresses are involved ♦ USSN 09/112,767; bend two outside layers are identical. This stability ♦ Care must be taken that the materials 09/112,768 actuator cancels bend due to ambient ♦ High speed, as a new drop do not delaminate temperature and residual stress. The can be fired before heat actuator only responds to transient dissipates heating of one side or the other. ♦ Cancels residual stress of formation Reverse The actuator loads a spring. When ♦ Better coupling to the ink ♦ Fabrication complexity ♦ USSN 09/113,097; spring the actuator is turned off, the spring ♦ High stress in the spring 09/113,077 releases. This can reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator A series of thin actuators are stacked. ♦ Increased travel ♦ Increased fabrication complexity ♦ Some piezoelectric stack This can be appropriate where ♦ Reduced drive voltage ♦ Increased possibility of short circuits ink jets actuators require high electric field due to pinholes ♦ USSN 09/112,803 strength, such as electrostatic and piezoelectric actuators. Multiple Multiple smaller actuators are used ♦ Increases the force ♦ Actuator forces may not add linearly, ♦ USSN 09/113,061; actuators simultaneously to move the ink. available from an actuator reducing efficiency 09/112,818; 09/113,096; Each actuator need provide only a ♦ Multiple actuators can be 09/113,095; 09/112,809; portion of the force required. positioned to control ink 09/112,794; 09/112,807; flow accurately 09/112,806 Linear A linear spring is used to transform a ♦ Matches low travel actuator ♦ Requires print head area for the ♦ USSN 09/112,772 Spring motion with small travel and high with higher travel spring force into a longer travel, lower force requirements motion. ♦ Non-contact method of motion transformation Coiled A bend actuator is coiled to provide ♦ Increases travel ♦ Generally restricted to planar ♦ USSN 09/112,815; actuator greater travel in a reduced chip area. ♦ Reduces chip area implementations due to extreme 09/112,808; 09/112,811; ♦ Planar implementations are fabrication difficulty in other 09/112,812 relatively easy to fabricate. orientations. Flexure bend A bend actuator has a small region ♦ Simple means of increasing ♦ Care must be taken not to exceed the ♦ USSN 09/112,779; actuator near the fixture point, which flexes travel of a bend actuator elastic limit in the flexure area 09/113,068; 09/112,754 much more readily than the ♦ Stress distribution is very uneven remainder of the actuator. The ♦ Difficult to accurately model with actuator flexing is effectively finite element analysis converted from an even coiling to an angular bend, resulting in greater travel of the actuator tip. Catch The actuator controls a small catch. ♦ Very low actuator energy ♦ Complex construction ♦ USSN 09/112,779 The catch either enables or disables ♦ Very small actuator size ♦ Requires external force movement of an ink pusher that is ♦ Unsuitable for pigmented inks controlled in a bulk manner. Gears Gears can be used to increase travel ♦ Low force, low travel ♦ Moving parts are required ♦ USSN 09/112,818 at the expense of duration. Circular actuators can be used ♦ Several actuator cycles are required gears, rack and pinion, ratchets, and ♦ Can be fabricated using ♦ More complex drive electronics other gearing methods can be used. standard surface MEMS ♦ Complex construction processes ♦ Friction, friction, and wear are possible Buckle plate A buckle plate can be used to change ♦ Very fast movement ♦ Must stay within elastic limits of the ♦ S. Hirata et al, “An a slow actuator into a fast motion. It achievable materials for long device life Ink-jet Head Using can also convert a high force, low ♦ High stresses involved Diaphragm Micro- travel actuator into a high travel, ♦ Generally high power requirement actuator”, Proc. medium force motion. IEEE MEMS, Feb. 1996, pp 418-423. ♦ USSN 09/113,096; 09/112,793 Tapered A tapered magnetic pole can increase ♦ Linearizes the magnetic ♦ Complex construction ♦ USSN 09/112,816 magnetic travel at the expense of force. force/distance curve pole Lever A lever and fulcrum is used to ♦ Matches low travel actuator ♦ High stress around the fulcrum ♦ USSN 09/112,755; transform a motion with small travel with higher travel 09/112,813; 09/112,814 and high force into a motion with requirements longer travel and lower force. The ♦ Fulcrum area has no linear lever can also reverse the direction of movement, and can be used travel. for a fluid seal Rotary The actuator is connected to a rotary ♦ High mechanical advantage ♦ Complex construction ♦ USSN 09/112,794 impeller impeller. A small angular deflection ♦ The ratio of force to travel ♦ Unsuitable for pigmented inks of the actuator results in a rotation of of the actuator can be the impeller vanes, which push the matched to the nozzle ink against stationary vanes and out requirements by varying the of the nozzle. number of impeller vanes Acoustic A refractive or diffractive (e.g. zone ♦ No moving parts ♦ Large area required ♦ 1993 Hadimioglu et lens plate) acoustic lens is used to ♦ Only relevant for acoustic ink jets al, EUP 550,192 concentrate sound waves. ♦ 1993 Elrod et al, EUP 572,220 Sharp A sharp point is used to concentrate ♦ Simple construction ♦ Difficult to fabricate using standard ♦ Tone-jet conductive an electrostatic field. VLSI processes for a surface ejecting point ink-jet ♦ Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the actuator changes, ♦ Simple construction in the ♦ High energy is typically required to ♦ Hewlett-Packard expansion pushing the ink in all directions. case of thermal ink jet achieve volume expansion. This leads Thermal Ink jet to thermal stress, cavitation, and ♦ Canon Bubblejet kogation in thermal ink jet implementations Linear, The actuator moves in a direction ♦ Efficient coupling to ink ♦ High fabrication complexity may be ♦ USSN 09/112,751; normal to normal to the print head surface. The drops ejected normal to the required to achieve perpendicular 09/112,787; 09/112,803; chip surface nozzle is typically in the line of surface motion 09/113,084; 09/113,077; movement. 09/112,816 Parallel to The actuator moves parallel to the ♦ Suitable for planar ♦ Fabrication complexity ♦ USSN 09/113,061; chip surface print head surface. Drop ejection fabrication ♦ Friction 09/112,818; 09/112,772; may still be normal to the surface. ♦ Stiction 09/112,754; 09/112,811; 09/112,812; 09/112,813 Membrane An actuator with a high force but ♦ The effective area of the ♦ Fabrication complexity ♦ 1982 Howkins push small area is used to push a stiff actuator becomes the ♦ Actuator size U.S. Pat. No. 4,459,601 membrane that is in contact with the membrane area ♦ Difficulty of integration in a VLSI ink. process Rotary The actuator causes the rotation of ♦ Rotary levers may be used ♦ Device complexity ♦ USSN 09/113,097; some element, such a grill or to increase travel ♦ May have friction at a pivot point 09/113,066; 09/112,818; impeller ♦ Small chip area 09/112,794 requirements Bend The actuator bends when energized. ♦ A very small change in ♦ Requires the actuator to be made ♦ 1970 Kyser et al This may be due to differential dimensions can be from at least two distinct layers, or to U.S. Pat. No. 3,946,398 thermal expansion, piezoelectric converted to a large motion. have a thermal difference across the ♦ 1973 Stemme expansion, magnetostriction, or other actuator U.S. Pat. No. 3,747,120 form of relative dimensional change. ♦ 09/112,802; 09/112,778; 09/112,779; 09/113,068; 09/112,780; 09/113,083; 09/113,121; 09/113,128; 09/113,127; 09/112,756; 09/112,754; 09/112,811; 09/112,812 Swivel The actuator swivels around a central ♦ Allows operation where the ♦ Inefficient coupling to the ink motion ♦ USSN 09/113,099 pivot. This motion is suitable where net linear force on the there are opposite forces applied to paddle is zero opposite sides of the paddle, e.g. ♦ Small chip area Lorenz force. requirements Straighten The actuator is normally bent, and ♦ Can be used with shape ♦ Requires careful balance of stresses ♦ USSN 09/113,122; straightens when energized. memory alloys where the to ensure that the quiescent bend is 09/112,755 austenic phase is planar accurate Double bend The actuator bends in one direction ♦ One actuator can be used to ♦ Difficult to make the drops ejected ♦ USSN 09/112,813; when one element is energized, and power two nozzles. by both bend directions identical. 09/112,814; 09/112,764 bends the other way when another ♦ Reduced chip size. ♦ A small efficiency loss compared to element is energized. ♦ Not sensitive to ambient equivalent single bend actuators. temperature Shear Energizing the actuator causes a ♦ Can increase the effective ♦ Not readily applicable to other ♦ 1985 Fishbeck shear motion in the actuator material. travel of piezoelectric actuator mechanisms U.S. Pat. No. 4,584,590 actuators Radial The actuator squeezes an ink ♦ Relatively easy to fabricate ♦ High force required ♦ 1970 Zoltan constriction reservoir, forcing ink from a single nozzles from glass ♦ Inefficient U.S. Pat. No. 3,683,212 constricted nozzle. tubing as macroscopic ♦ Difficult to integrate with VLSI structures processes Coil/uncoil A coiled actuator uncoils or coils ♦ Easy to fabricate as a ♦ Difficult to fabricate for non-planar ♦ USSN 09/112,815; more tightly. The motion of the free planar VLSI process devices 09/112,808; 09/112,811; end of the actuator ejects the ink. ♦ Small area required, ♦ Poor out-of-plane stiffness 09/112,812 therefore low cost Bow The actuator bows (or buckles) in the ♦ Can increase the speed of ♦ Maximum travel is constrained ♦ USSN 09/112,819; middle when energized. travel ♦ High force required 09/113,096; 09/112,793 ♦ Mechanically rigid Push-Pull Two actuators control a shutter. One ♦ The structure is pinned at ♦ Not readily suitable for ink jets ♦ USSN 09/113,096 actuator pulls the shutter, and the both ends, so has a high which directly push the ink other pushes it. out-of-plane rigidity Curl A set of actuators curl inwards to ♦ Good fluid flow to the ♦ Design complexity ♦ USSN 09/113,095; inwards reduce the volume of ink that they region behind the actuator 09/112,807 enclose. increases efficiency Curl A set of actuators curl outwards, ♦ Relatively simple ♦ Relatively large chip area ♦ USSN 09/112,806 outwards pressurizing ink in a chamber construction surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes enclose a volume of ♦ High efficiency ♦ High fabrication complexity ♦ USSN 09/112,809 ink. These simultaneously rotate, ♦ Small chip area ♦ Not suitable for pigmented inks reducing the volume between the vanes. Acoustic The actuator vibrates at a high ♦ The actuator can be ♦ Large area required for efficient ♦ 1993 Hadimioglu et vibration frequency. physically distant from the operation at useful frequencies al, EUP 550,192 ink ♦ Acoustic coupling and crosstalk ♦ 1993 Elrod et al, EUP ♦ Complex drive circuitry 572,220 ♦ Poor control of drop volume and position None In various ink jet designs the actuator ♦ No moving parts ♦ Various other tradeoffs are required ♦ Silverbrook, EP 0771 does not move. to eliminate moving parts 658 A2 and related patent applications ♦ Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal way that ink jets ♦ Fabrication simplicity ♦ Low speed ♦ Thermal ink jet tension are refilled. After the actuator is ♦ Operational simplicity ♦ Surface tension force relatively small ♦ Piezoelectric ink jet energized, it typically returns rapidly compared to actuator force ♦ USSN-09/112,751; to its normal position. This rapid ♦ Long refill time usually dominates 09/113,084; 09/112,779; return sucks in air through the nozzle the total repetition rate 09/112,816; 09/112,819; opening. The ink surface tension at 09/113,095; 09/112,809; the nozzle then exerts a small force 09/112,780; 09/113,083; restoring the meniscus to a minimum 09/113,121; 09/113,122; area. This force refills the nozzle 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Shuttered Ink to the nozzle chamber is ♦ High speed ♦ Requires common ink pressure ♦ USSN 09/113,066; oscillating provided at a pressure that oscillates ♦ Low actuator energy, as the oscillator 09/112,818; 09/112,772; ink pressure at twice the drop ejection frequency. actuator need only open or ♦ May not be suitable for pigmented 09/112,815; 09/113,096; When a drop is to be ejected, the close the shutter, instead of inks 09/113,068; 09/112,808 shutter is opened for 3 half cycles: ejecting the ink drop drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main actuator has ejected a ♦ High speed, as the nozzle is ♦ Requires two independent actuators ♦ USSN 09/112,778 actuator drop a second (refill) actuator is actively refilled per nozzle energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive The ink is held a slight positive ♦ High refill rate, therefore a ♦ Surface spill must be prevented ♦ Silverbrook, EP 0771 ink pressure pressure. After the ink drop is high drop repetition rate is ♦ Highly hydrophobic print head 658 A2 and related ejected, the nozzle chamber fills possible surfaces are required patent applications quickly as surface tension and ink ♦ Alternative for: USSN pressure both operate to refill the 09/112,751; 09/112,787; nozzle. 09/112,802; 09/112,803; 09/113,097; 09/113,099; 09/113,084; 09/112,799; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,819; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet channel to the nozzle ♦ Design simplicity ♦ Restricts refill rate ♦ Thermal ink jet channel chamber is made long and relatively ♦ Operational simplicity ♦ May result in a relatively large chip ♦ Piezoelectric ink jet narrow, relying on viscous drag to ♦ Reduces crosstalk area ♦ USSN 09/112,807; reduce inlet back-flow. ♦ Only partially effective 09/112,806 Positive ink The ink is under a positive pressure, ♦ Drop selection and ♦ Requires a method (such as a nozzle ♦ Silverbrook, EP 0771 pressure so that in the quiescent state some of separation forces can be rim or effective hydrophobizing, or 658 A2 and related the ink drop already protrudes from reduced both) to prevent flooding of the patent applications the nozzle. ♦ Fast refill time ejection surface of the print head. ♦ Possible operation of This reduces the pressure in the the following: nozzle chamber which is required to ♦ USSN 09/112,751; eject a certain volume of ink. The 09/112,787; 09/112,802; reduction in chamber pressure results 09/112,803; 09/113,097; in a reduction in ink pushed out 09/113,099; 09/113,084; through the inlet. 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,816; 09/112,819; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; Baffle One or more baffles are placed in the ♦ The refill rate is not as ♦ Design complexity ♦ HP Thermal Ink Jet inlet ink flow. When the actuator is restricted as the long inlet ♦ May increase fabrication complexity ♦ Tektronix energized, the rapid ink movement method. (e.g. Tektronix hot melt Piezoelectric piezoelectric ink jet creates eddies which restrict the flow ♦ Reduces crosstalk print heads). through the inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible flap In this method recently disclosed by ♦ Significantly reduces back- ♦ Not applicable to most ink jet ♦ Canon restricts inlet Canon, the expanding actuator flow for edge-shooter configurations (bubble) pushes on a flexible flap thermal ink jet devices ♦ Increased fabrication complexity that restricts the inlet. ♦ Inelastic deformation of polymer flap results in creep over extended use Inlet filter A filter is located between the ink ♦ Additional advantage of ink ♦ Restricts refill rate ♦ USSN 09/112,803; inlet and the nozzle chamber. The filtration ♦ May result in complex construction 09/113,061; 09/113,083; filter has a multitude of small holes ♦ Ink filter may be fabricated 09/112,793; 09/113,128; or slots, restricting ink flow. The with no additional process 09/113,127 filter also removes particles which steps may block the nozzle. Small inlet The ink inlet channel to the nozzle ♦ Design simplicity ♦ Restricts refill rate ♦ USSN 09/112,787; compared to chamber has a substantially smaller ♦ May result in a relatively large chip 09/112,814; 09/112,820 nozzle cross section than that of the nozzle, area resulting in easier ink egress out of ♦ Only partially effective the nozzle than out of the inlet. Inlet shutter A secondary actuator controls the ♦ Increases speed of the ink- ♦ Requires separate refill actuator and ♦ USSN 09/112,778 position of a shutter, closing off the jet print head operation drive circuit ink inlet when the main actuator is energized. The inlet is The method avoids the problem of ♦ Back-flow problem is ♦ Requires careful design to minimize ♦ USSN 09/112,751; located inlet back-flow by arranging the ink- eliminated the negative pressure behind the paddle 09/112,802; 09/113,097; behind the pushing surface of the actuator 09/113,099; 09/113,084; ink-pushing between the inlet and the nozzle. 09/112,779; 09/113,077; surface 09/112,816; 09/112,819; 09/112,809; 09/112,780; 09/113,121; 09/112,794; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,765; 09/112,767; 09/112,768 Part of the The actuator and a wall of the ink ♦ Significant reductions in ♦ Small increase in fabrication ♦ USSN 09/113,084; actuator chamber are arranged so that the back-flow can be achieved complexity 09/113,095; 09/113,122; moves to motion of the actuator closes off the ♦ Compact designs possible 09/112,764 shut off the inlet. inlet Nozzle In some configurations of ink jet, ♦ Ink back-flow problem is ♦ None related to ink back-flow on ♦ Silverbrook, EP 0771 actuator does there is no expansion or movement eliminated actuation 658 A2 and related not result in of an actuator which may cause ink patent applications ink back-flow through the inlet. ♦ Valve-jet back-flow ♦ Tone-jet

NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles are fired ♦ No added complexity on ♦ May not be sufficient to displace ♦ Most ink jet systems nozzle periodically, before the ink has a the print head dried ink ♦ USSN 09/112,751; firing chance to dry. When not in use the 09/112,787; 09/112,802; nozzles are sealed (capped) against 09/112,803; 09/113,097; air. 09/113,099; 09/113,084; The nozzle firing is usually 09/112,778; 09/112,779; performed during a special clearing 09/113,077; 09/113,061; cycle, after first moving the print 09/112,816; 09/112,819; head to a cleaning station. 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Extra power In systems which heat the ink, but do ♦ Can be highly effective if ♦ Requires higher drive voltage for ♦ Silverbrook, EP 0771 to ink heater not boil it under normal situations, the heater is adjacent to the clearing 658 A2 and related nozzle clearing can be achieved by nozzle ♦ May require larger drive transistors patent applications over-powering the heater and boiling ink at the nozzle. Rapid The actuator is fired in rapid ♦ Does not require extra ♦ Effectiveness depends substantially ♦ May be used with: succession of succession. In some configurations, drive circuits on the print head upon the configuration of the ink jet USSN 09/112,751; actuator this may cause heat build-up at the ♦ Can be readily controlled nozzle 09/112,787; 09/112,802; pulses nozzle which boils the ink, clearing and initiated by digital logic 09/112,803; 09/113,097; the nozzle. In other situations, it may 09/113,099; 09/113,084; cause sufficient vibrations to 09/112,778; 09/112,779; dislodge clogged nozzles. 09/113,077; 09/112,816; 09/112,819; 09/113,095; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Extra power Where an actuator is not normally ♦ A simple solution where ♦ Not suitable where there is a hard ♦ May be used with: to ink driven to the limit of its motion, applicable limit to actuator movement USSN 09/112,802; pushing nozzle clearing may be assisted by 09/112,778; 09/112,819; actuator providing an enhanced drive signal 09/113,095; 09/112,780; to the actuator. 09/113,083; 09/113,121; 09/112,793; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Acoustic An ultrasonic wave is applied to the ♦ A high nozzle clearing ♦ High implementation cost if system ♦ USSN 09/113,066; resonance ink chamber. This wave is of an capability can be achieved does not already include an acoustic 09/112,818; 09/112,772; appropriate amplitude and frequency ♦ May be implemented at actuator 09/112,815; 09/113,096; to cause sufficient force at the nozzle very low cost in systems 09/113,068; 09/112,808 to clear blockages. This is easiest to which already include achieve if the ultrasonic wave is at a acoustic actuators resonant frequency of the ink cavity. Nozzle A microfabricated plate is pushed ♦ Can clear severely clogged ♦ Accurate mechanical alignment is ♦ Silverbrook, EP 0771 clearing against the nozzles. The plate has a nozzles required 658 A2 and related plate post for every nozzle. A post moves ♦ Moving parts are required patent applications through each nozzle, displacing ♦ There is risk of damage to the dried ink nozzles ♦ Accurate fabrication is required Ink pressure The pressure of the ink is ♦ May be effective where ♦ Requires pressure pump or other ♦ May be used with ink pulse temporarily increased so that ink other methods cannot be pressure actuator jets covered by USSN streams from all of the nozzles. This used ♦ Expensive 09/112,751; 09/112,787; may be used in conjunction with ♦ Wasteful of ink 09/112,802; 09/112,803; actuator energizing. 09/113,097; 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,738; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Print head A flexible ‘blade’ is wiped across the ♦ Effective for planar print ♦ Difficult to use if print head surface ♦ Many ink jet systems wiper print head surface. The blade is head surfaces is non-planar or very fragile usually fabricated from a flexible ♦ Low cost ♦ Requires mechanical parts polymer, e.g. rubber or synthetic ♦ Blade can wear out in high volume elastomer. print systems Separate ink A separate heater is provided at the ♦ Can be effective where ♦ Fabrication complexity ♦ Can be used with boiling nozzle although the normal drop e- other nozzle clearing many ink jets covered by heater ection mechanism does not require it. methods cannot be used USSN 09/112,751; The heaters do not require individual ♦ Can be implemented at no 09/112,787; 09/112,802; drive circuits, as many nozzles can additional cost in some 09/112,803; 09/113,097; be cleared simultaneously, and no inkjet configurations 09/113,099; 09/113,084; imaging is required. 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages Examples Electro- A nozzle plate is separately ♦ Fabrication simplicity ♦ High temperatures and pressures are ♦ Hewlett Packard formed fabricated from electroformed nickel, required to bond nozzle plate Thermal ink jet nickel and bonded to the print head chip. ♦ Minimum thickness constraints ♦ Differential thermal expansion Laser ablated Individual nozzle holes are ablated ♦ No masks required ♦ Each hole must be individually ♦ Canon Bubblejet or drilled by an intense UV laser in a nozzle ♦ Can be quite fast formed ♦ 1988 Sercel et al., polymer plate, which is typically a polymer ♦ Some control over nozzle ♦ Special equipment required SPIE, Vol. 998 such as polyimide or polysulphone profile is possible ♦ Slow where there are many Excimer Beam ♦ Equipment required is thousands of nozzles per print head Applications, pp. 76- relatively low cost ♦ May produce thin burrs at exit holes 83 ♦ 1993 Watanabe et al., U.S. Pat. No. 5,208,604 Silicon A separate nozzle plate is ♦ High accuracy is attainable ♦ Two part construction ♦ K. Bean, IEEE micro- micromachined from single crystal ♦ High cost Transactions on machined silicon, and bonded to the print head ♦ Requires precision alignment Electron Devices, wafer. ♦ Nozzles may be clogged by adhesive Vol. ED-25, No. 10, 1978, pp 1185-1195 ♦ Xerox 1990 Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass capillaries are drawn from ♦ No expensive equipment ♦ Very small nozzle sizes are difficult ♦ 1970 Zoltan capillaries glass tubing. This method has been required to form U.S. Pat. No. 3,683,212 used for making individual nozzles, ♦ Simple to make single ♦ Not suited for mass production but is difficult to use for bulk nozzles manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is deposited as a ♦ High accuracy (<1 μm) ♦ Requires sacrificial layer under the ♦ Silverbrook, EP 0771 surface layer using standard VLSI deposition ♦ Monolithic nozzle plate to form the nozzle 658 A2 and related micro- techniques. Nozzles are etched in the ♦ Low cost chamber patent applications machined nozzle plate using VLSI lithography ♦ Existing processes can be ♦ Surface may be fragile to the touch ♦ ussn 09/112,751; using VLSI and etching. used 09/112,787; 09/112,803; lithographic 09/113,077; 09/113,061; processes 09/112,815; 09/113,096; 09/113,095; 09/112,809; 09/113,083; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820 Monolithic, The nozzle plate is a buried etch stop ♦ High accuracy (<1 μm) ♦ Requires long etch times ♦ ussn 09/112,802; etched in the wafer. Nozzle chambers are ♦ Monolithic ♦ Requires a support wafer 09/113,097; 09/113,099; through etched in the front of the wafer, and ♦ Low cost 09/113,084; 09/113,066; substrate the wafer is thinned from the back ♦ No differential expansion 09/112,778; 09/112,779; side. Nozzles are then etched in the 09/112,818; 09/112,816; etch stop layer. 09/112,772; 09/112,819; 09/113,068; 09/112,808; 09/112,780; 09/113,121; 09/113,122 No nozzle Various methods have been tried to ♦ No nozzles to become ♦ Difficult to control drop position ♦ Ricoh 1995 Sekiya et plate eliminate the nozzles entirely, to clogged accurately al U.S. Pat. No. prevent nozzle clogging. These ♦ Crosstalk problems 5,412,413 include thermal bubble mechanisms ♦ 1993 Hadimioglu et and acoustic lens mechanisms al EUP 550,192 ♦ 1993 Elrod et al EUP 572,220 Trough Each drop ejector has a trough ♦ Reduced manufacturing ♦ Drop firing direction is sensitive to ♦ USSN 09/112,812 through which a paddle moves. complexity wicking. There is no nozzle plate. ♦ Monolithic Nozzle slit The elimination of nozzle holes and ♦ No nozzles to become ♦ Difficult to control drop position. ♦ 1989 Saito et al instead of replacement by a slit encompassing clogged accurately U.S. Pat. No. 4,799,068 individual many actuator positions reduces ♦ Crosstalk problems nozzles nozzle clogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Edge Ink flow is along the surface of the ♦ Simple construction ♦ Nozzles limited to edge ♦ Canon Bubblejet (‘edge chip, and ink drops are ejected from ♦ No silicon etching required ♦ High resolution is difficult 1979 Endo et al GB shooter’) the chip edge. ♦ Good heat sinking via ♦ Fast color printing requires one print patent 2,007,162 substrate head per color ♦ Xerox heater-in-pit ♦ Mechanically strong 1990 Hawkins et al ♦ Ease of chip handing U.S. Pat. No. 4,899,181 ♦ Tonejet Surface Ink flow is along the surface of the ♦ No bulk silicon etching ♦ Maximum ink flow is severely ♦ Hewlett-Packard TIJ (‘roof chip, and ink drops are ejected from required restricted 1982 Vaught et al shooter’) the chip surface, normal to the plane ♦ Silicon can make an U.S. Pat. No. 4,490,728 of the chip. effective heat sink ♦ USSN 09/112,787, ♦ Mechanical strength 09/113,077; 09/113,061; 09/113,095; 09/112,809 Through Ink flow is through the chip, and ink ♦ High ink flow ♦ Requires bulk silicon etching ♦ Silverbrook, EP 0771 chip, drops are ejected from the front ♦ Suitable for pagewidth 658 A2 and related forward (‘up surface of the chip. print heads patent applications shooter’) ♦ High nozzle packing ♦ USSN 09/112,803; density therefore low 09/112,815; 09/113,096; manufacturing cost 09/113,093; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Through Ink flow is through the chip, and ink ♦ High ink flow ♦ Requires wafer thinning ♦ USSN 09/112,751; chip, drops are ejected from the rear ♦ Suitable for pagewidth ♦ Requires special handling during 09/112,802; 09/113,097; reverse surface of the chip. print heads manufacture 09/113,099; 09/113,084; (‘down ♦ High nozzle packing 09/113,066; 09/112,778; shooter’) density therefore low 09/112,779; 09/112,818; manufacturing cost 09/112,816; 09/112,772; 09/112,819; 09/113,068; 09/112,808; 09/112,780; 09/113,121; 09/113,122 Through Ink flow is through the actuator, ♦ Suitable for piezoelectric ♦ Pagewidth print heads require several ♦ Epson Stylus actuator which is not fabricated as part of the print heads thousand connections to drive circuits ♦ Tektronix hot melt same substrate as the drive ♦ Cannot be manufactured in standard piezoelectric ink jets transistors. CMOS fabs ♦ Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink which typically ♦ Environmentally friendly ♦ Slow drying ♦ Most existing ink jets dye contains: water, dye, surfactant, ♦ No odor ♦ Corrosive ♦ USSN 09/112,751; humectant, and biocide. ♦ Bleeds on paper 09/112,787; 09/112,802; Modern ink dyes have high water- ♦ May strikethrough 09/112,803; 09/113,097; fastness, light fastness ♦ Cockles paper 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 ♦ Silverbrook, EP 0771 658 A2 and related patent applications Aqueous, Water based ink which typically ♦ Environmentally friendly ♦ Slow drying ♦ USSN 09/112,787; pigment contains: water, pigment, surfactant, ♦ No odor ♦ Corrosive 09/112,803; 09/112,808; humectant, and biocide. ♦ Reduced bleed ♦ Pigment may clog nozzles 09/113,122; 09/112,793; Pigments have an advantage in ♦ Reduced wicking ♦ Pigment may clog actuator 09/113,127 reduced bleed, wicking and ♦ Reduced strikethrough mechanisms ♦ Silverbrook, EP 0771 strikethrough. ♦ Cockles paper 658 A2 and related patent applications ♦ Piezoelectric ink-jets ♦ Thermal ink jets (with significant restrictions) Methyl Ethyl MEK is a highly volatile solvent ♦ Very fast drying ♦ Odorous ♦ USSN 09/112,751; Ketone used for industrial printing on ♦ Prints on various substrates ♦ Flammable 09/112,787; 09/112,802; (MEK) difficult surfaces such as aluminum such as metals and plastics 09/112,803; 09/113,097; cans. 09/113,099; 09/113,084; 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Alcohol Alcohol based inks can be used ♦ Fast drying ♦ Slight odor ♦ USSN 09/112,751; (ethanol, 2- where the printer must operate at ♦ Operates at sub-freezing ♦ Flammable 09/112,787; 09/112,802; butanol, and temperatures below the freezing temperatures 09/112,803; 09/113,097; others) point of water. An example of this is ♦ Reduced paper cockle 09/113,099; 09/113,084; in-camera consumer photographic ♦ Low cost 09/113,066; 09/112,778; printing. 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Phase The ink is solid at room temperature, ♦ No drying time- ink ♦ High viscosity ♦ Tektronix hot melt change and is melted in the print head before instantly freezes on the ♦ Printed ink typically has a ‘waxy’ piezoelectric ink jets (hot melt) jetting. Hot melt inks are usually print medium feel ♦ 1989 Nowak wax based, with a melting point ♦ Almost any print medium ♦ Printed pages may ‘block’ U.S. Pat. No. 4,820,346 around 80° C. After jetting the ink can be used ♦ Ink temperature may be above the ♦ USSN 09/112,751; freezes almost instantly upon ♦ No paper cockle occurs curie point of permanent magnets 09/112,787; 09/112,802; contacting the print medium or a ♦ No wicking occurs ♦ Ink heaters consume power 09/112,803; 09/113,097; transfer roller. ♦ No bleed occurs ♦ Long warm-up time 09/113,099; 09/113,084; ♦ No strikethrough occurs 09/113,066; 09/112,778; 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Oil Oil based inks are extensively used ♦ High solubility medium for ♦ High viscosity: this is a significant ♦ USSN 09/112,751; in offset printing. They have some dyes limitation for use in inkjets, which 09/112,787; 09/112,802; advantages in improved ♦ Does not cockle paper usually require a low viscosity. Some 09/112,803; 09/113,097; characteristics on paper (especially ♦ Does not wick through short chain and multi-branched oils 09/113,099; 09/113,084; no wicking or cockle). Oil soluble paper have a sufficiently low viscosity. 09/113,066; 09/112,778; dies and pigments are required. ♦ Slow drying 09/112,779; 09/113,077 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 Micro- A microemulsion is a stable, self ♦ Stops ink bleed ♦ Viscosity higher than water ♦ USSN 09/112,751; emulsion forming emulsion of oil, water, and ♦ High dye solubility ♦ Cost is slightly higher than water 09/112,787; 09/112,802; surfactant. The characteristic drop ♦ Water, oil, and amphiphilic based ink 09/112,803; 09/113,097; size is less than 100 nm, and is soluble dies can be used ♦ High surfactant concentration 09/113,099; 09/113,084; determined by the preferred ♦ Can stabilize pigment required (around 5%) 09/113,066; 09/112,778; curvature of the surfactant. suspensions 09/112,779; 09/113,077; 09/113,061; 09/112,818; 09/112,816; 09/112,772; 09/112,819; 09/112,815; 09/113,096; 09/113,068; 09/113,095; 09/112,808; 09/112,809; 09/112,780; 09/113,083; 09/113,121; 09/113,122; 09/112,793; 09/112,794; 09/113,128; 09/113,127; 09/112,756; 09/112,755; 09/112,754; 09/112,811; 09/112,812; 09/112,813; 09/112,814; 09/112,764; 09/112,765; 09/112,767; 09/112,768; 09/112,807; 09/112,806; 09/112,820; 09/112,821 

We claim:
 1. A method of manufacture of an ink jet printhead which includes: providing a substrate; depositing a doped layer on the substrate and etching said layer to create an array of nozzles on the substrate with a nozzle chamber in communication with each nozzle; and utilizing planar monolithic deposition, lithographic and etching processes to create a paddle arranged in each nozzle chamber, each paddle being connected to a thermal bend actuator unit and the thermal bend actuator unit comprising a plurality of thermal bend devices arranged in spaced, parallel relationship.
 2. A method of manufacturing an ink jet printhead as claimed in claim 1 wherein multiple ink jet printheads are formed simultaneously on the substrate.
 3. A method of manufacturing an ink jet printhead as claimed in claim 1 wherein said substrate is a silicon wafer.
 4. A method of manufacturing an ink jet printhead as claimed in claim 1 wherein integrated drive electronics are formed on the same substrate.
 5. A method of manufacturing an ink jet printhead as claimed in claim 4 wherein said integrated drive electronics are formed using a CMOS fabrication process.
 6. A method of manufacturing an ink jet printhead as claimed in claim 1 wherein ink is ejected from said substrate normal to said substrate.
 7. A method of manufacture of an ink jet printhead arrangement including a series of nozzle chambers, said method comprising the steps of: (a) utilising an initial semiconductor wafer having an electrical circuitry layer formed thereon; (b) etching said electrical circuitry layer so as to define a nozzle chamber area; (c) depositing and etching a first sacrificial layer, said etching defining a series of nozzle chamber walls and an actuator anchor point; (d) depositing a first heater material layer; (e) depositing an intermediate material layer; (f) etching said first heater material layer and said intermediate material layer to define portions of an actuator, ejection paddle and nozzle chamber walls; (g) depositing and etching a second sacrificial layer, said etching including etching a cavity defining a portion of the nozzle chamber walls; (h) depositing and etching a further glass layer to define the roof of the nozzle chamber and the walls thereof; (i) etching an ink supply channel through said wafer to form a fluid communication with said nozzle chamber; and (j) etching away remaining sacrificial material.
 8. A method as claimed in claim 7 wherein said intermediate layer comprises substantially glass.
 9. A method as claimed in claim 7 wherein said first heater material layer comprises substantially Titanium Nitride.
 10. A method as claimed in claim 7 wherein said steps further include the step of etching anti-wicking notches in the surface of said circuitry layer.
 11. A method as claimed in claim 7 further including the step of depositing corrosion barriers over portions of said arrangement so as to reduce corrosion effects.
 12. A method as claimed in claim 7 wherein the etching of layers includes etching vias so as to allow for the electrical interconnection of portions of subsequent layers.
 13. A method as claimed in claim 7 wherein said wafer comprises a double side polished CMOS wafer.
 14. A method as claimed in claim 7 wherein said step (j) comprises a through wafer etch from a back surface of said wafer.
 15. A method as claimed in claim 7 wherein step (j) is also utilized to simultaneously separate said wafer into separate printheads. 